import pygame
from pygame.sprite import Sprite


class Ship(Sprite):
    def __init__(self,screen,ai_settings):
        """初始化飞船并设置其初始位置"""
        super().__init__()
        self.screen = screen

        #加载图像并获取外接矩阵
        self.image = pygame.image.load('images/hero1.png')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()

        #将每艘新飞船放在屏幕中央
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom

        #再飞船的属性center中存储小数值
        self.center = float(self.rect.centerx)

        #移动标志
        self.moving_right = False
        self.moving_left = False

        self.ai_settings = ai_settings


    def blitme(self):
        """指定位置绘制飞船"""
        self.screen.blit(self.image,self.rect)

    def update(self):
        """根据移动标志调整飞船的位置"""
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left > 0:
            self.center -= self.ai_settings.ship_speed_factor

        #根据self.center更新rect对象
        self.rect.centerx = self.center
    
    def center_ship(self):
        """让飞船在屏幕中居中"""
        self.center = self.screen_rect.centerx
    
